Movement damping apparatus

ABSTRACT

A movement damping apparatus has magnetorheological fluid that is pressed through a flow path forming a bottleneck in order to dampen a movement. The flow path is divided into at least two flow tracks by a partition that forms an additional friction surface.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to an apparatus in which a magnetorheologicalfluid (MRF) is forced through a flow path, preferably in order to damp amovement, with a unit which produces a magnetic field being provided,and with the magnetic field acting on the magnetorheological fluid (MRF)in the area of the flow path.

Apparatuses with magnetorheological fluids are known per se. Theadvantage is that the damping effect can be influenced by varying themagnetic field. Energy-damping apparatuses are advantageously and/ornecessarily used in motor vehicles, not only in the chassis, but also ona range of other components, for example on steering columns, headrests,safety belts, seats and seat elements, etc. Apparatuses such as theseare likewise used in other vehicles, for example for the front and rearwheel suspension, in the saddle support, or the like, on cycles. Theyare likewise used in various sports devices, such as running shoes orski boots.

Apparatuses such as these are particularly advantageous when it ispossible in this way to produce large pressure differences (with orwithout a magnetic field), and high maximum pressures resulting fromthem.

This can advantageously be achieved by partition walls in the flowchannel through which the magnetic field passes, which partition wallssubdivide the flow path and multiply the friction area, withoutexcessively increasing the physical space required.

In this case, EP 1270989 A1 may be cited as prior art, where themagnetic field is produced by a coaxial coil and acts on amagnetorheological fluid in a plurality of annular, concentric channels,which are formed by annular partition walls.

One major disadvantage of embodiments according to the prior art is thecoil core, which represents a “magnetic bottleneck” which impedesminiaturization. The entire magnetic flux has to pass through the corein the center of the coil, whose cross-sectional area, through which themagnetic field can pass, decreases with the square of the coil diameterwhen the latter is reduced in size. However, because of magneticsaturation, only certain flux densities are worthwhile and possible inthe core, in the range from 1.5 to 2 Tesla, depending on the material.

The radially externally located channels thus produce a poor area ratiowith respect to the internal core, which becomes ever poorer as the corediameter is reduced with the channel cross section remaining the same.

One major disadvantage of the prior art is the varying magnetic fluxdensity in the flow channels, because the area through which themagnetic field passes increases from the inside outward, as a result ofwhich the magnetic flux density decreases severely radially outward (byabout half in the case of EP1270989A1). Different flux densities resultin different viscosity changes and different pressures, as a result ofthis, in the flow channels, and this can lead to deformation of thepartition walls. It is magnetically advantageous for the wallthicknesses of the partition walls and the distances between thepartition walls to be kept small (in the region of 0.1 mm to 1 mm).Since the fan surface area is large (fans occur only in one sense,because the fans are intended to enlarge the friction area) large forcesoccur on the partition walls even when the pressure differences aresmall. The (thin) fans can also, inter alia, result from the deformationand this can then lead to a magnetic short and therefore to even greaterfield strength differences. The correct operation of the apparatus isthen no longer ensured.

A further disadvantage of the prior art is that the two sections of achannel through which the magnetic field passes—seen in the flowdirection—are physically separated from one another. MRF particles whichflow through the channel pass the areas in the magnetic field and formchains there (=viscosity change), but the chains are detached again inthe neutral area between the fields.

The time required for chain formation shortens the effective channellength, since the MRF effect does not occur completely during chainformation. Particularly at high flow rates, the time for chain formationmust be taken into account, optionally to be compensated for by longerchannels. However, longer channels in turn exacerbate the problem ofmagnetic saturation of the core.

In certain applications, in which the flow of MRF is intended to beblocked completely, it is disadvantageous for the flow channel to bearranged as a plurality of annular, concentric channels. In order toprevent MRF from breaking (flowing) through, the magnetic field must notbe less than a certain value at its weakest point in the channel.

This weakest point occurs radially on the outside, where the fluxdensity is lowest. The flux density required for a certain fieldstrength in the radially outermost channel produces a considerablyhigher flux density in the innermost channel, however, since the areathrough which the flux passes is smaller.

On the one hand, this can increase the energy demand of the system sincevery high flux densities are required in the inner area or, on the otherhand, produce weak points where the MRF can break through because thefield strength required to block the channel is not reached. The fieldstrength cannot be increased indefinitely in order to ensure that theradially outermost channel has a high flux density, since othercomponents can be saturated.

The described disadvantages of a system according to the prior art alsorelate in the same sense to US 2005087408 A1. The damper describedtherein uses a coaxial coil to produce a magnetic field which is eithershorted by the fans, and therefore does not reach the radially outermostareas or, when the fans are not magnetically permeable, decreasesstrongly radially outward because of the large air gap and themultiplication of the area through which the flux passes.

In WO2007/149393 A2, the magnetic field always runs parallel to theflowing medium, thus resulting in a reduced viscosity change in the MRF,since large pressure differences can be achieved only when the magneticlines of force run at right angles to the flow direction. There is alsono magnetic return path. In consequence, this design is not veryefficient.

Particularly at high pressure levels, very small magnetic-fielddistribution differences in the fan elements to which pressure isapplied result in severe deformation (defects). Operation is then nolonger ensured. In designs according to the prior art, this deformationwould become ever greater since the unit which produces the magneticfield has a very poor ratio with respect to the radially outermost fanchannel.

DE 198 20 570 (Carl Schenk AG) discloses annular fans. These are subjectto the same disadvantages as mentioned initially, specifically differenteffective area size, a changing magnetic field and a changing pressure.

The mixing of bypass channels and blocking channels located alongsideone another, as described on page 3 of DE 198 20 570, is thus impossiblein the case of MRF and magnetic fields. In the case of designsconfigured for electrorheological fluids, the electrical field passesfrom one plate to the other (−pole to +pole) and is closed via a cable,while in the case of MRF applications, the magnetic field must flow backfrom a magnetic-field producing unit through a large number of elementsand then via a magnetic return path to the unit that produces it (themagnetic field is closed), in which case these parts shouldadvantageously have the same cross-sectional areas of magneticallypermeable materials. It is therefore technically incorrect to use ERFand MRF apparatuses of the same design.

In EP 1 270 989 and US 2005 087 408, the fan extends over the entirelength, when seen in the flow direction. However, this is associatedwith the disadvantage that the fan walls located between the fansegments through which the magnetic flux passes increase the basicfriction (basic pressure), thus reducing the spreading (=differencebetween switched on and switched off). In the switched-on state, thisfan section achieves nothing, because no magnetic field passes throughit. This design is therefore disadvantageous.

These disadvantages can be prevented in an apparatus according to theinvention, thus allowing miniaturization of the system and theconstruction of more efficient damping apparatuses.

In one preferred embodiment, this is achieved in that:

-   -   the pole surfaces are substantially flat, and    -   lie parallel to the flow direction of the MRF, and    -   the switchable MRF channel has the magnetic field applied to it        without interruption, seen in the flow direction, and    -   in this case, the flow path which is located between the pole        surfaces is subdivided into at least two flow sections by at        least one substantially flat partition wall composed of        preferably ferromagnetic material.

The partition walls have approximately the same width, thus resulting ina homogeneous magnetic field. However, this is dependent on the lines offorce of the magnetic field running substantially at right anglesthrough the partition walls.

Therefore, contrary to the prior art, the magnetic field in the channelis no longer interrupted when a coil is used whose axis runs at rightangles to the flow direction. Furthermore, the ratio of the core areathrough which the flux passes to the channel area through which the fluxpasses is highly advantageous, since these areas can be approximatelythe same. Substantially the same flux passes through the individualchannels. One major feature of the invention is therefore that themagnetic field strength or the flux density produced by themagnetic-field producing unit (coil, core), is virtually the same(homogeneous) via the fans (partition walls), the channels and thesheath via which the magnetic field flows back to the producing unit.This therefore results in the same viscosity change in themagnetorheological fluid in the individual channels which are influencedby the magnetic field, and the channels with respect to one another,therefore resulting substantially in the same pressure.

According to Hagen-Poiseuille's law, the volume flow, that is to say thevolume which flows through a tube per unit time in the case of laminarflow of a homogeneous viscous fluid, is dependent on the fourth power ofthe radius of the tube. The extreme dependency of the flow resistance onthe unobstructed width of the tube is also evident in non-cylindricalchannels and applies even with restrictions for non-Newtonian fluids.

Since there are generally design restrictions for indefinitedimensioning of flow paths with sheathing friction surfaces, this oftenresults in the problem of having to achieve high flow resistances, as aresult of which movement damping cannot be achieved to the desiredextent.

BRIEF SUMMARY OF THE INVENTION

In order to overcome these difficulties, the invention now proposes thatthe flow path is subdivided by at least one partition wall, which formsan additional friction surface, into at least two flow sections. Theflow path has a sheath, that is to say it is formed within a tube,channel or the like. It preferably represents an outlet channel of acontainer which contains the fluid. This means that, although thepartition wall creates only two additional friction surfaces, theirinfluence on the flow resistance is, however, far greater than simpleduplication, since the unobstructed width of the sheath which bounds theflow path is approximately halved. In particular, the additionalfriction surfaces are flat.

In one preferred embodiment, a plurality of partition walls are joinedtogether parallel to one another in at least one pack, as a result ofwhich the effect described above is also considerably reinforced.

The damping can therefore be set in a wide range by means of themagnetic field and, with a maximum magnetic field, it is even possibleto block the passage of the magnetorheological fluid up to a pressure of60 bar, preferably up to 400 bar, and this has also been done. MRFvalves according to the prior art generally operate only with maximumpressures of around 30 bar.

The design features described above are not known, and are thereforealso not obvious, from the prior art cited above. The optimization of anapparatus such as this which is essential for correct and advantageousoperation of the apparatus requires that the viscosity be changed in avery short time by building up and varying the magnetic field. Theprofile of the lines of force, the cross-sectional shape, the choice ofmaterial, the pressure response, deformation, the physical spacerequirement etc. do not represent a choice of self-evident equivalentoptions, but are the result of intensive investigations and experiments.It is not simply by chance that there are no details relating to this inthe prior art.

Furthermore, the invention is distinguished by a compact design, whichis particularly advantageous when the spatial conditions are confinedand/or there is a requirement for a low weight (for example in cycledesign).

In a first embodiment, the pack can also be formed from partition wallswhich extend parallel to the flow sections and are kept separated byupright lugs, in particular bent-up edge lugs. The pack can be heldtogether via any desired connection on the lugs, direct adhesivebonding, soldering, adhesive strips or the like. For example, 16partition walls with a thickness of 0.2 mm can be provided, whichsubdivide the outlet channel into 17 flow sections of 0.2 mm. The outletchannel therefore has an unobstructed height of 6.6 mm in the area ofthe friction surfaces. Instead of having to join the pack together fromindividual elements, it is also feasible to produce the partition wallpack integrally, for example from plastic or metal, by injectionmolding, die casting or the like.

In a further embodiment, at least one partition wall may extend on across-sectional plane of the outlet channel and may have slots whichform the flow sections, with the slot walls representing the additionalfriction surfaces. A partition wall such as this may be produced as astamped sheet metal part, as a sintered part or as ametal-injection-molded (MIM) part, in which case, for example, itappears to be like a ladder or comb. The remaining webs between theslots can preferably extend on both sides of a central connecting web.

In order to achieve any desired flow section length, a plurality of suchpartition walls can in this embodiment be arranged in a row close to oneanother, with the slots being aligned.

In a further embodiment, the pack may have a cavity which is continuousover the length and extends centrally in the flow path. This embodimentmakes it possible to pass a component through the pack which is arrangedin the flow path. By way of example, this component may be a cable, apiston rod or the like, when a piston which forces the fluid out of thecontainer is pulled rather than pushed.

The formation according to the invention of additional friction surfacesis particularly advantageous when a device is provided which produces avariable magnetic field and has pole surfaces in the flow path, viawhich pole surfaces the magnetic field acts on the magnetorheologicalfluid in order to control the flow rate, with the friction surfaces ofeach partition wall forming parallel pole surfaces in addition to thepole surfaces.

Each partition wall admittedly reduces the cross-sectional area of theoutlet channel and therefore the volume of fluid which can be magnetizedper unit time, but results in a higher pressure difference due to thereduced distances between two respective pole surfaces, despite thedimensions remaining the same. A plurality of partition walls aretherefore preferably joined together to form a pack, and are insertedinto the outlet channel. The distances between the pole surfaces thatgovern the strength of the magnetization are so small in this pack thatthe height of the outlet channel can be enlarged, in order to match theflow cross section of the constriction to the volume to be magnetized ofthe magnetorheological fluid to be forced through. If required, whenthere are a multiplicity of pole surfaces at a short distance from oneanother, the constriction may even have a larger free cross-sectionalarea than the container; in this case, the constriction even forms awidened area.

An embodiment which is particularly advantageous and can be producedeasily is one in which the partition walls are stamped from transformerlaminate and are lacquered on the mutually touching surfaces. Thelacquering insulates the individual laminates from one another, as aresult of which eddy currents that are created cannot accumulate.

In order to make it possible to influence the viscosity of themagnetorheological fluid by means of a magnetic field such that the flowresistance of the constriction changes, various criteria must besatisfied. A magnetic field produced by a coil must be introduced intothe magnetorheological fluid, for which purpose elements and parts ofthe apparatus which are provided for the lines of force to pass directlythrough the magnetorheological fluid should be more highly magneticallypermeable than other elements and parts which are outside the directpath of the lines of force. Additional pole surfaces that are introducedin this case increase the concentration of the magnetic field on theparticles which interact with the magnetic field in themagnetorheological fluid. In this case, turbulence in the flow should beavoided as far as possible, and should at least should not be promoted,in order to improve the effect. The installation of partition wallswhich have a smooth surface that does not promote turbulence istherefore preferable. Flat surfaces are particularly suitable. Uprightwebs or edges are disadvantageous. In contrast to this, layers whichincrease the friction are advantageous.

A coil which is associated with the sheath on the outside of the flowpath is therefore provided with a core composed of a magneticallypermeable material, such as transformer laminate, ferrite powder, etc.,which is referred to in the following text as the coil core material, inparticular an iron core which, for example, is C-shaped. The flow pathis passed through the gap which remains between the pole surfaces of theC-shaped core. Those walls of the sheath of the flow path which rest onthe pole surfaces are composed of magnetically highly permeable materialwhile, in contrast, the side walls are composed of a material which isat least less permeable than the magnetorheological fluid.

The invention makes it possible to provide the sheathing of the flowpath with a cylindrical cross section in a simple manner. In thisembodiment, the apparatus comprises a continuous cylindrical tube, inwhich the constriction is formed by the installation of the partitionwall, but in particular naturally by the installation of a pack ofpartition walls as described above, with in each case one element, whichhas a cross section in the form of a circle segment, and is composed ofcoil core material, being associated with the pack on both sides as atermination, such that the cylindrical tube is filled. Since the coilrests externally with the pole surfaces of the iron core, thecylindrical tube is composed in particular of a material which ismagnetically impermeable or is at least less permeable than themagnetorheological fluid to be forced through the flow sections, inorder to prevent a magnetic short via the tube wall. The pack itself canalso be constructed such that its magnetic permeability complies withthis requirement, for example by partition walls which extend parallelto the flow sections and are composed of coil core material beingseparated from one another by webs composed of material which is atleast less magnetically permeable.

If, as described above, the partition walls are stamped from the coilcore material, then the remaining webs cannot consist of a materialwhich is magnetically less permeable; however, it has been found thatthe webs are magnetically saturated, if appropriately minimized, suchthat the magnetic field is nevertheless adequately forced through theflow sections. Alternatively, cutouts can advantageously be provided inthe partition walls, through which holders composed of magneticallypoorly permeable or non-permeable material are passed, and which keepthe partition walls separated from one another.

In a further preferred embodiment, which represents a highlyspace-saving design, the device which produces the variable magneticfield has a core around which a coil is wound, which core forms thepartition wall which is arranged in the flow path, with the coil axisbeing at right angles to the flow sections, and with the flow pathhaving a sheath composed of magnetically permeable material. Thepartition walls are preferably joined together in two packs, which arearranged on both sides of the core around which the coil is wound. Thecore, which is arranged between the two packs of partition walls, ispreferably in the form of an approximately cuboid block around which thecoil winding is placed, whose axis extends through the flow path, atright angles to the flow direction. The core within the coil canlikewise contain flow sections if the coil is wound three-dimensionallyand leaves the inlet and outlet openings of the flow sections free.

An embodiment having two three-dimensionally wound coils which arelocated symmetrically on the inside and each have an element which is inthe form of a circle segment as a core, and which rests on the inside ofthe tube is particularly preferable. A pack of partition walls is rangedbetween the two cores and, as already mentioned above, may have acontinuous cavity. This embodiment is also particularly advantageouswhen the container and outlet channel are manufactured integrally from acontinuous cylindrical tube.

If the coil and core form a central partition wall and a pack ofpartition walls is arranged on both sides, then both packs are in turncompleted by an element made of coil core material which has a crosssection in the form of a circle segment and whose curved surfaces reston the inside of the tube. In contrast to the embodiment described abovewith an externally arranged coil, the tube in this embodiment iscomposed of coil core material, in order to directly close the magneticcircuit without additional elements.

Starting from the core of the coil approximately in the center of theflow path, the lines of force therefore run at right angles outwardthrough the flow section and a pack of partition walls with additionalpole surfaces, and an element which is in the form of a circle segment,into the cylindrical tube, from which they return diametrically oppositethrough the second element which is in the form of a circle segment andthe second flow section and a second pack of partition walls into thecore which is wound around and is arranged in the center.

In the case of the apparatus according to the invention, the internalpart (coil, partition walls, core) of the device can be moved axially ina cylindrical tube in order to produce the variable magnetic field. Inthis case, the internal parts can advantageously be pulled or pushed bymeans of a piston rod, through the hole in which parts the cable for thepower supply can be passed, or can be moved by means of a cable.

The invention will now be described in more detail in the following textwith reference to the figures in the attached drawings, in which:

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows a schematic view of an oscillation damping apparatus of arear-wheel suspension arm of a cycle,

FIG. 2 shows a longitudinal section through the connecting line shown inFIG. 1,

FIG. 3 shows a cross section through the flow path shown in FIG. 2,

FIG. 4 shows a schematic oblique view of a first embodiment of theapparatus according to the invention,

FIG. 5 shows an end view of a first embodiment of the apparatus as shownin FIG. 4, with the profile of the lines of force of a magnetic field,

FIG. 6 a shows a partially sectioned oblique view of a third embodimentwithout tangential edges,

FIG. 6 b shows a partially sectioned oblique view of a third embodimentwith tangential edges,

FIG. 7 shows an oblique view of a pack of partition walls of a firstembodiment,

FIG. 8 shows an end view of the embodiment as shown in FIG. 6,

FIG. 9 shows a second embodiment of a partition wall,

FIG. 10 shows an enlarged side view of a pack of partition walls of thesecond embodiment,

FIG. 11 shows an oblique view of a second embodiment of a magnet coil,

FIG. 12 shows a cross section through a further embodiment of theapparatus with a magnetic coil as shown in FIG. 11,

FIG. 13 shows a partial longitudinal section through a fourth embodimentof the apparatus,

FIGS. 14 and 15 show two circuit diagrams for the operation of theapparatus according to the invention, and

FIG. 16 shows a perspective view of a partition wall stack withindividual partition wall coils.

DESCRIPTION OF THE INVENTION

As is shown in FIG. 1, a movement damping apparatus may be provided, forexample, on the rear wheel suspension arm of a cycle, with a container 1containing a piston 53, which is fixed to the frame of the cycle bymeans of a piston rod. The container 1 is filled with a fluid, forexample a magnetorheological fluid, above the piston. A spring or a gasfilling 55 which acts as a spring is arranged under the piston 53. Anequalizing container 51 is furthermore fixed to the rear-wheelsuspension arm, and the fluid can be forced out of the container 1 viathe connecting line 52 into the equalizing container 51. The equalizingcontainer contains a piston 54 and, under the piston 54, likewise aspring or a gas filling 56 which acts as a spring. A constriction 4 isprovided in the connecting line 52 and produces an opposing forceagainst the fluid flowing over it, thus resulting in damping. The figuredoes not show the unit for producing a variable magnetic field.

FIG. 2 shows a longitudinal section through the line 52. Theconstriction 4 is formed by a pack 17 of flat partition walls 15 whichis inserted into the flow path 5, and between which partition walls 15 amultiplicity of flow sections 16 remain. If the flow path 5 is sheathedby a cylindrical tube which represents a part of the line 52, then anupper and a lower element 23 in the form of circle segments are fittedto the pack 17 of partition walls 15 and rest on the inside of the line52. The flat partition walls 15 each have two additional frictionsurfaces for the fluid, which result in a very high flow resistance overa short length in the flow path.

FIG. 3 shows a further embodiment of the partition wall pack 17. In thiscase, the partition walls 15 are provided cohesively in a plastic ormetal injection-molded part or die-cast part, which can be inserted intoa tube or line as an integral element. The pack 17 has a central cavity21 through which, for example, a line, a cable, a rod or the like can bepassed.

If the movement damping process is intended to be made dependent on anycriteria, then a magnetorheological fluid can be used, which is forcedthrough the flow path 5 and whose flow characteristics can be influencedby a device 2 for producing a variable magnetic field. In this case, thepartition walls are preferably formed from a magnetically permeablematerial, as a result of which the friction surfaces also form polesurfaces when a magnet coil 7 with a core 6 is provided, and whose polesurfaces 11, 12 are parallel to the friction surfaces. In this case, thecoil 7 is arranged such that its axis is at right angles to the flowsections 16 between the partition walls 15.

Details of another embodiment can be seen better in FIGS. 4 and 5. Inparticular, a container 1 is cylindrical and contains a movable piston,by means of which the magnetorheological fluid 3 is forced through theflow path. The subsequent outlet channel has an approximatelyrectangular cross section, and the flow path 4 is subdivided bypartition walls 15, which are composed of a highly permeable coil corematerial and two of which are shown in FIG. 4, into flow sections 16which have a considerably shorter height, although they have the samewidth. The device 2 which produces the magnetic field in this embodimenthas a coil 7 which is provided with a C-shaped core 6 composed of amagnetically highly permeable coil core material, for example iron, andwhose axis is at right angles to the flow direction of themagnetorheological fluid 3 in the flow path 5 and the flow sections 16formed by the partition walls 15. The C-shaped core 6 can also becomposed of laminates, in particular transformer laminates.

In addition to iron as a very good material with good “magnetic”characteristics, the following may also be used as coil core materials:

Silicon-iron, a relatively good material with good magneticcharacteristics, poor electrical conductivity and very low remanance,

magnetic steel, a material which costs somewhat more, does not corrodeand has somewhat poorer magnetic characteristics,

nickel-iron, a traditional soft-magnetic alloy which costs more and hasa very high permeability, and

iron-cobalt, as the most expensive material, but with the highestsaturation flux density.

Depending on the installation location, other materials are possible(for example a core composed of ferrite, iron powder or other powdermixtures). More “exotic” materials may offer advantages (for exampleBASF Catamold FN50; which is compatible with injection molding).

The C-shaped core 6 has flat, mutually parallel pole surfaces 11, 12,between which the outlet channel is passed. The magnetic permeability ofthe magnetorheological fluid 3 is less than that of the core 6, as aresult of which the strength of the magnetic field indicated by thelines of force 10 in FIG. 5 is dependent on the height of the gapbetween the pole surfaces 11, 12. Every partition wall 15 reduces theheight and forms additional flat pole surfaces 13, 14. If only onepartition wall 15 is provided, then the pole surfaces 11 and 14 areassociated with the upper flow section 16, and the pole surfaces 13 and12 are associated with the lower flow section 16. Every further flowsection 16 located in between can be influenced by pole surfaces 13 and14 of two partition walls 15. In the embodiment shown in FIG. 4, theflow path 5 is provided in that section of the outlet channel whichpasses the core 6 with three flow sections 16 which occupy virtually theentire width. In the embodiment shown in FIG. 5, the side walls 8 of theoutlet channel are composed, at least within the flow path 5, of amagnetically at least poorly permeable material, and the partition walls15 composed of coil core material are separated from one another by webs22, which are likewise composed of a magnetically at least poorlypermeable material.

FIG. 7 shows partition walls 15 which have bent lugs 18 on the twolongitudinal side edges, which lugs 18 keep the partition walls 15separated, with the partitions walls 15 bounding a multiplicity of flowsections 16. The partition walls 15 are connected to form a pack 17 viathe lugs 18 by adhesive bonding, soldering or the like, which pack 17can be pushed as a unit into the outlet channel. By way of example, thepartition walls 15 are composed of a transformer laminate, that is tosay a material with very high magnetic permeability, and the pack 17shown in FIG. 7 in each case comprises sixteen partition walls 15 andflow sections 16, which all have the same thickness or height of, forexample, 0.2 mm. The pack 17 therefore has an overall thickness of 6.4(6.2) mm.

FIGS. 6 and 8 to 10 show an embodiment in which the magnet coilarrangement is provided in the interior of the flow path 5. FIG. 6 showsan oblique view, sectioned at an angle, of the outlet channel,illustrated in the form of a cylindrical tubular piece with a threadedcollar 27. The container 1, which is likewise formed by a tubular pieceof the same diameter, is screwed into the threaded collar 27. Theconstriction 4 at the start of the flow path 5 is formed by awedge-shaped center web 25 of an insert 24, as a result of which themagnetorheological fluid 3 which emerges from the container 1 issubdivided into two flow elements 26. The coil arrangement 2 has amagnet coil 7, whose axis is at right angles to the flow path 5 and isarranged centrally in the outlet channel such that it is covered by thewedge-shaped center web 25 (FIG. 8). The core 6 is once again arrangedwithin the coil 7, with the core 6 in this embodiment being cuboid andbeing adjacent on both sides to a pack 17 of partition walls 15 with amultiplicity of flow sections 16, as is described in FIG. 7 or, in thefollowing text, with reference to FIGS. 9 and 10. A permanent magnet ora combination of permanent magnets and soft-magnetic materials may beused as the core. An element 23 which is approximately in the form of acircle segment (pole cap) is in each case fitted as a termination foreach pack 17, which element 23 is manufactured from coil core materialand rests on the inside of the cylindrical outlet channel.

In this embodiment, the outlet channel is likewise produced from a coilcore material, for example from an iron tube or the like, in order toclose the magnetic lines of force 10. The electrical connecting lines 28are passed out of the outlet channel, in a manner which is notillustrated in any more detail, at the outlet-side end.

As already mentioned with reference to FIG. 7, the pack 17 may becomposed of partition walls 15 which extend in the longitudinaldirection of the flow path 5. FIGS. 9 and 10 show a second possible wayto design a pack 17 of partition walls 15 with flow sections 16. In thiscase, each partition wall 15 extends on a radial plane at right anglesthrough the outlet channel, and the flow sections 16 are composed ofslots 19 which are incorporated in the partition walls 15. A partitionwall 15 such as this may, in particular, be stamped from a transformerlaminate or the like, with a multiplicity of slots 19 being separatedfrom one another by webs 20 which project from a central connecting web22 (FIG. 9). The slots 19 thus extend toward the edge, and are coveredby side parts of the insert 24. Connecting webs 22 could, of course,also be provided on both edges, with the slots 19 extending between themwithout any center interruption. As is shown in FIG. 10, a plurality ofpartition walls 15 are arranged directly one behind the other, with theslots 19 being aligned. In this case, the slot walls represent theadditional pole surfaces 13, 14.

It is also feasible for the partition wall pack to be in the form of afolded element.

Manufacturing by stamping from transformer laminate or the like alsomakes it possible to produce the coil core 6, both packs 17 of partitionwalls 15 and the terminating elements 23, which are in the form ofcircle segments, for matching to the cylindrical cross section of theoutlet channel 5 in one piece, which is then in the form shown in FIG.9. Those side surfaces of the partition walls 15 which rest on oneanother can be provided with an electrically insulating lacquer, suchthat eddy currents which are created in the individual partition walls15 do not accumulate. The part 30 shown in FIG. 10 is fitted with thecoil 7 and is inserted into the insert 24, which is then introduced intothe outlet channel or the line 52, and is axially fixed. The insert 24is composed of a magnetically poorly permeable material, for example aplastic.

FIGS. 11 and 12 show two embodiments, in which the coil 7 is woundthree-dimensionally, that is to say each winding is not located on aplane but is composed of a plurality of sections, with in each case oneapproximately semicircular section 33 being routed upward or downwardbetween the straight sections 32 which extend in the longitudinaldirection of the flow path 5 in the outlet channel. The coil 7 istherefore open at the ends, and a part 30 as shown in FIG. 12 can have acentral cavity 21 through which, for example, the pulling meansmentioned above can be passed to the piston or base of the container 1.However, the cavity 21 may also be used to hold a connecting element forthe pack 17 of partition walls 15, or the cable 34 that is shown inFIG. 1. Since the coil 7 is spread out at the ends, the core 6 may alsohave flow sections 16 within the coil 7 which are formed by slots 19between aligned webs 20.

The form shown in FIG. 11 may also be created for the two coils 7, as isindicated in FIG. 12. In this embodiment, each of the two coils 7 isassociated with the element 23, which is in the form of a circlesegment, as a core, with a pack 17 of partition walls 15 being arrangedbetween the two elements 23 and having flow sections 16 and a centralcavity 21. The insert 24 is annular and is inclined toward the container1, forming the constriction 4 (FIG. 6).

The device which is arranged in the magnetorheological fluid 3 or in theflow path 5 and is designed to produce the variable magnetic field mayalso comprise a printed circuit board with a planar coil and a core, inwhich case even further electronic components for controlling the device2 may also be arranged on the printed circuit board.

The coils 7 may be manufactured not only from an insulated copper wirebut also from a copper strip, a copper foil or an anodized aluminumfoil.

FIG. 13 shows an embodiment in which a container-like closure 37 isfitted, forming a seal, to the container 1, at one of whose ends theflow path is provided, in which case the container 1 and the closure 37can be pushed one inside the other in order to reduce the internal area.The closure 37 is provided with a sensor 38, with which a lengthmeasurement scale on the container 1 is associated, such that thesliding movement can be recorded. Furthermore, the closure 37 isprovided with a pressure sensor 39, thus allowing the magnetic field ofthe internal coil 7 within the flow path 5 to be varied as a function ofpressure and/or position. By way of example, this embodiment could beused in a saddle support of a cycle.

FIG. 14 shows an example of a simple, pulsed drive (PWM), in which thecoil current can be varied. In the simplest form, the switch S may be amechanical switch/push button; it is advantageous to use a transistor.However, other options are also feasible, such as a relay or elsespecial forms of the transistor (MOSFET, IGBT). Inter alia, the switchmay also be provided in the GND branch, that is to say between the coiland ground (GND). The resistor Rs is intended to symbolize the option ofcurrent measurement. This can be done in addition to measurement via ashunt by other methods such as a current transformer or an integratedsolution (current measurement—IC, Hall sensor). The current can bemeasured at any desired point in the circuit. The diode D is afreewheeling diode, which allows the coil 7 to continue to drive currentafter S has been opened. The diode can likewise be replaced by a switch(Sync-FET).

In addition to the simple control-system option, the control system canalso be equipped with various sensors which make it possible to form aclosed loop. Depending on the purpose, pressure, force, position,temperature, speed or acceleration sensors, for example, may be used. Itis also feasible to combine these or other sensors.

FIG. 15 shows an example of a drive by means of a full bridge(H-bridge). The coil L can thus be driven in both directions, that is tosay the polarity at the coil connections can be changed. By way ofexample, this allows a permanent magnet in the magnetic circuit of thecoil to be used for reinforcement or attenuation. In the case of apulsed drive (PWM), the coil current can be varied. The resistor Rs isintended to symbolize the option of current measurement. This can bedone in addition to measurement via a shunt by other methods such as acurrent transformer or an integrated solution (current measurement-IC,Hall sensor). The location of the current measurement may vary, and, forexample, measurement in the ground (GND) branch is advantageous, inorder to obtain a measurement signal that is referenced to GND. Interalia, duplicated measurement, for example upstream of S2 and upstream ofS4, may also offer advantages since this results in the current beingmeasured in each half-bridge arm (fault detection). In addition to thesimple control-system option, the control system in this embodiment mayalso be equipped with various sensors which make it possible to form aclosed loop. Depending on the purpose, pressure, force, position,temperature, speed or acceleration sensors, for example, may be used. Itis also feasible to combine these or other sensors.

FIG. 16 shows an exemplary embodiment of a partition wall stack in whichthe flow path is subdivided into a plurality of flow sections 16 bypartition walls 15′ which are arranged at a distance from one another.One of these flow sections is illustrated by way of example in FIG. 12,together with an indication of the flow direction.

In this exemplary embodiment, each partition wall 15′ composed ofmagnetically permeable or ferromagnetic material has its own associatedpartition wall coil 7′, which in each case consists of only a singleturn. By way of example, this turn may be formed by an insulatedconductor.

Electrically, the individual partition wall coils are connected inseries, with the output of the respective partition wall coil 7′ locatedabove being connected to the input of the partition wall coil 7′ locatedbelow. The contact points are annotated 35.

These partition wall coils 7′ may be provided alternatively or inaddition to the coil 7 in the previous figures. If they are providedonly as an alternative to this coil, then these partition wall coilstogether form this coil 7.

At least on the inlet-flow side or outlet-flow side, the turn ispreferably at most as high as the partition wall itself, thus notimpeding the flow through. The coil may be higher on the side surfaces.The spacers 34 (for example formed in the insulation of the partitionwall coil 7′) and the contacts 35 may also be arranged here. The coilturn may also be composed of an anodized aluminum foil. It is alsopossible to apply this turn to a printed circuit board. The printedcircuit boards are then stacked as a multilayer.

The partition walls 15′ are preferably composed of magneticallypermeable, ferromagnetic material, and form the core of the individualpartition wall coils.

The core (6), the partition walls (15) and the sheath may each bepartially or entirely in the form of permanent magnets. For thispurpose, they are at least partially manufactured from materials such asmagnetic iron alloys or steel alloys, ferrite, AlNiCo, rare earths suchas SmCo and NeFeB. Manufacture is also feasible in combination withother materials, for example as is the case with plastic-bonded magnets.

If these partition wall individual coils are used, the coil—as alreadymentioned—from the previous exemplary embodiments with the referencenumber 7 may be omitted. This results in a weight and space advantage.However, both coils, specifically the coil 7 and the partition wallcoils 7′, may be used for particularly strong magnetic fields.

The invention claimed is:
 1. A movement damping apparatus, comprising: an amount of magnetorheological fluid to be forced through a flow path, the flow path forming a constriction in order to damp a movement; a magnet unit configured to produce a magnetic field acting on said magnetorheological fluid via pole surfaces effective in said flow path; and at least one substantially flat partition wall disposed to divide said flow path into at least two substantially flat flow sections, said at least one partition wall forming an additional friction surface in said flow path; and wherein said magnet unit and said flow path are relatively configured such that, when a maximum magnetic field is applied, a passage of the magnetorheological fluid through said flow sections is blocked.
 2. The apparatus according to claim 1, wherein a shape of all said friction surfaces in said through-channel is substantially the same.
 3. The apparatus according to claim 1, wherein a magnetic field strength or a flux density is substantially identical in all of the flow sections.
 4. The apparatus according to claim 1, wherein said additional friction surfaces are planar surfaces.
 5. The apparatus according to claim 1, wherein said partition wall is one of a plurality of partition walls joined together parallel to one another in at least one stack.
 6. The apparatus according to claim 5, which comprises spacers holding said partition walls separate from one another and extending parallel to said flow sections.
 7. The apparatus according to claim 1, wherein said partition wall extends on a cross-sectional plane of said flow path and said partition wall is formed with slots defining said flow sections, with said slots having slot walls representing said additional friction surfaces.
 8. The apparatus according to claim 1, which comprises a cylindrical sheath encasing said flow path, and elements formed as circle segments with curved surfaces and defining said pole surfaces, said curved surfaces of said elements being matched to an inner wall of said sheath.
 9. The apparatus according to claim 1, wherein said magnet unit is disposed to generate a magnetic field with flux lines running substantially at right angles through said flow sections.
 10. The apparatus according to claim 1, wherein said magnet unit is a device configured to produce a variable magnetic field having a core and a coil wound around said core, said core forming said partition wall disposed in said flow path, and a coil axis extending at right angles to said flow sections, and wherein said flow path is defined within a sheath composed of magnetically permeable material.
 11. The apparatus according to claim 1, wherein said partition walls are stamped from transformer laminate and are insulated, at least on mutually touching surfaces.
 12. The apparatus according to claim 1, wherein said magnet unit is a device configured to produce a variable magnetic field having a core and a coil wound around said core, said core being formed with flow channels and said coil is wound leaving inlet and outlet openings of said flow channels free.
 13. The apparatus according to claim 1, wherein a core of said magnet unit, said partition wall, pole caps, and a container are at least partially formed of or with a material selected from the group consisting of magnetic iron alloys or steel alloys, ferrite, AlNiCo, and rare earths.
 14. The apparatus according to claim 13, wherein said core of said magnet unit, said partition wall, said pole caps, and said container are at least partially formed of or with a material selected from the group consisting of SmCo and NeFeB).
 15. A bicycle, comprising a frame, a suspension fork, a rear structure, and an apparatus according to claim 1 disposed between said frame and said suspension fork or said rear structure. 